Comment 2 for bug 1678563

It's not totally related to this issue, but I think GenericCheck also can be enhanced by interpreting right-hand side.

I excerpt from the official docs

     <some_attribute>:%(user.id)s

     The value on the right-hand side is either a string or resolves to a string using regular
     Python string substitution. The available attributes and values are dependent on the program
     that is using the common policy engine.

%(user.id) would be resolved to a string, but I found list type like $(tags) would not be considered.